Rotary brushing tools are widely used in industry for cleaning, polishing, deburring, finishing and burnishing metals and other materials. Rotary brushes are typically constructed from individual tufts of bristle material (which may be wire or non-metallic materials such as Tampico, horsehair, nylon, and the like) which is folded in half to form a loop. The loop is used to anchor the tufts in a rotatable hub. The loops are anchored by staples or by looping them through perforations in a disk or around an annular ring. Brush constructions of this type are shown, for example, in U.S. Pat. No. 4,092,758. Other methods of anchoring the bristles, such as by thermoplastic bands, as shown for example in U.S. Pat. No. 2,190,206, are also known.
Regardless of how the bristles are anchored in the hub in prior art brushes, the bristles are almost without exception inserted into the hub in the form of individual tufts or placed in bundles around an annular ring. This is wasteful of bristle material in at least two respects. First, the need to bend the bristles in half to form a loop requires extra material in the loop. Second, because of the folding step, the ends of the bristles do not form a tuft of uniform length; the bristles on the inside of the loop will be longer than the bristles on the outside of the loop. Thus, the bristles need to be longer than actually required so that they can be trimmed to the desired length after the tufts are formed and inserted into the hub.
A good brushing tool should provide a uniform distribution of bristles at the periphery of the tool. Tuft type brushes do not provide a uniform distribution of bristles. In addition, a good brushing tool must not clamp the bristle excessively, such as by rings or staples, which would reduce the cross-sectional area of the bristle at the clamp zone. This clamping or over-clamping action causes pinpoint stress, which may cause the bristle to break prematurely. Finally, a good brushing tool should not allow the bristle to rub against a metal side plate, which also leads to breakage.
It is an object of the present invention to provide a method and apparatus for manufacturing a rotary brushing tool in which the filaments are secured to the hub in such a manner as to avoid stresses on the bristles which may cause premature breakage of the bristles.
It is another object of the present invention to provide a method of making a rotary brush which requires relatively few manual or mechanical steps in securing the bristles to the hub.
It is another object of the present invention to provide a method and apparatus for making a rotary brush in which the bristles are distributed with a uniform density around the circumference of the hub, and with minimum waste of the length of the bristles.